Adjustable resource management system

ABSTRACT

A resource allocation request that includes a usage type identifier and requested amount of a resource is received where the usage type identifier is associated with a group identifier. Adjustable resource configuration information is accessed to obtain: (1) a maximum associated with the usage type identifier, (2) a minimum associated with the usage type identifier, and (3) a group limit associated with the group identifier. Resource state information is accessed and it is determined whether to grant the resource allocation request based at least in part on the maximum, the minimum, the group limit, and the resource state information. If so, the resource allocation request is granted. If not, the resource allocation request is denied.

BACKGROUND OF THE INVENTION

System resources (such as buffers or other memory) which are sharedamongst multiple processes and/or devices are often allocated anddeallocated depending upon the needs of the requestor. For example, thecommands malloc( ) and free( ) are used to request the allocation ofmemory and free allocated memory, respectively. New resource allocationsystems and/or techniques which improve the performance of the systemwould be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a flowchart illustrating an embodiment of a process toallocate resources in an adjustable manner.

FIG. 2 is a block diagram illustrating an embodiment of a storage systemwith an adjustable resource management module.

FIG. 3 is a block diagram illustrating an embodiment of an adjustableresource management module.

FIG. 4A shows two tables illustrating embodiments of adjustable resourceconfiguration information for hardware resources and firmware resources,respectively.

FIG. 4B is a diagram illustrating an embodiment of a change to thenumber of usage types and groups.

FIG. 5 is a diagram illustrating an embodiment of resource stateinformation and associated allocation communications.

FIG. 6 is a diagram illustrating an embodiment of a deallocation messagethat originates from a resource.

FIG. 7 is a graph illustrating an embodiment of a maximum associatedwith a host write usage type that is adjusted.

FIG. 8 is a flowchart illustrating an embodiment of a process to adjustthe resource configuration information in response to real time usage.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

Various embodiments of an adjustable resource management system aredescribed herein. In some embodiments, one or more resource requestors(e.g., identified by type identifiers) are grouped and those groupedresource requestors share a pool of resources (e.g., hardware resourcesor firmware resources). In one example, the resource may be a buffer inhardware and resource requestors which want to use the buffer aregrouped together. The groups and associated limits (e.g., maximums orminimums) may be stored in resource configuration information which isadjustable. For example, a limit may be adjusted on-the-fly (e.g., ifsome resource requestors are more active than others), a new group maybe created, a resource requestor may be moved to a different group, etc.The following figure describes one embodiment of an adjustable resourcemanagement process which is performed by a resource management module.

FIG. 1 is a flowchart illustrating an embodiment of a process toallocate resources in an adjustable manner. In some embodiments, theprocess is performed by a resource management module or a controllertherein. In some embodiments, the resource management module is separatefrom and/or external to a plurality of central processing units (CPU).In contrast, some other systems may have one or more of the CPUs beingresponsible for resource management and/or allocation.

At 100, a resource allocation request that includes a usage typeidentifier and requested amount of a resource is received, wherein theusage type identifier is associated with a group identifier. Forexample, the requested amount may specify the number or amount of thedesired resource that is being requested. The type identifier (e.g.,uniquely) identifies which process or device (sometimes referred toherein as a (resource) requestor) sent the resource request. In someembodiments, the resource being requested is a hardware resource (e.g.,a resource in hardware or associated with hardware) or a firmwareresource (e.g., a resource in firmware or associated with firmware).

In this example, resource requestors are grouped into groups of one ormore resource requestors, where resource requestors in the same groupshare a specified amount of a given resource. As will be described inmore detail below, in some embodiments, some groups may have only asingle resource requestor (and therefore do not need to share the poolof resources associated with that group) whereas other groups havemultiple resource requestors. Each group is (e.g., uniquely) identifiedby a group identifier.

At 102, adjustable resource configuration information is accessed toobtain: (1) a maximum associated with the usage type identifier, (2) aminimum associated with the usage type identifier, and (3) a group limitassociated with the group identifier. For example, the adjustableresource configuration information may store which resource requestors(e.g., identified by usage type identifier) are part of which group,maximums and minimums for each resource requestor, and the group limitsfor each group.

At 104, resource state information is accessed. For example, theresource state information may record what resources are currentlyallocated or not. In some embodiments, the resource state informationalso records the usage type identifier for each allocated resource.

At 106, it is determined whether to grant the resource allocationrequest based at least in part on the (e.g., usage type) maximum, the(e.g., usage type) minimum, the group limit, and the resource stateinformation. In one example, in order for the resource allocationrequest to be granted, neither the (e.g., usage type) maximum nor thegroup limit can be exceeded by the requested amount, nor can the minimumbe violated for other usage types in the same group. Naturally, thereneeds to be a sufficient amount of free resources available to beallocated. In some embodiments, other factors or considerations are alsotaken into account (i.e., not exceeding the maximum or the group limitare necessary but not sufficient conditions for the request to begranted).

If it is decided to grant (108), the resource allocation request isgranted at 112. For example, the resource state information is updatedto reflect the allocation of the requested resources and applicableand/or related information is stored (e.g., in some embodiments, thetype identifier). A grant communication is sent from the adjustableresource management module to the resource requestor. If not, theresource allocation request is denied at 110. For example, a denialcommunication is sent from the adjustable resource management module tothe resource requestor.

It may be helpful to give an example of an adjustable resourcemanagement system that performs the process of FIG. 1 in a specificapplication. The following figure describes one such example system in astorage application.

FIG. 2 is a block diagram illustrating an embodiment of a storage systemwith an adjustable resource management module. In some embodiments, theadjustable resource management module (200) shown here performs theprocess of FIG. 1. In some embodiments, the adjustable resourcemanagement module (200) is implemented at least in part on hardware(e.g., an application-specific integrated circuit (ASIC), afield-programmable gate array (FPGA), or a general-purpose integratedcircuit (e.g., a microcontroller). In some other embodiments, theadjustable resource management module (200) is implemented at least inpart using computer instructions (e.g., a computer program productembodied in a non-transitory computer readable medium, firmware(computer) instructions, etc.).

In this example, the adjustable resource management module (200) is partof a storage controller (202). The storage controller (202) receivesinstructions (e.g., read instructions, write instructions, eraseinstructions, etc.) from a host (204) that are directed to and/orassociated with storage (206). In some embodiments, the storage includessolid state storage (e.g., Flash).

The storage controller (202) in this example has firmware resources(208) and hardware resources (210) that are managed by the adjustableresource management module (200). For example, the adjustable resourcemanagement module (200) may receive a resource allocation request forfirmware resources (208) or hardware resources (210) from any of theCPUs (212 a-212 b). The adjustable resource management module (200) thenperforms the process of FIG. 1 to determine whether to grant or deny therequest.

Storage systems tend to grow in storage capacity and complexity. Forexample, one way to increase the storage capacity of solid state storagesystems is to increase the number of bits stored per cell. Single-levelcell (SLC), multi-level cell (MLC), tri-level cell (TLC), and quad-levelcell (QLC) configurations store one (1) bit through four (4) bits permemory cell, respectively. As the number of bits per cell increases,more complex error correction decoders (e.g., low-density parity-check(LDPC) decoders) and in general more processing resources are needed.This, in turn, may require storage controllers to have multiple CPUs.

Some previous storage controllers with multiple CPUs had resourceallocation management (e.g., of firmware resources (208) and hardwareresources (210)) performed amongst the CPUs. To support this, theseother storage controllers had to perform handshaking between the CPUs tomanage management of the resources. In contrast, the exemplary storagecontroller (202) shown here offloads resource management from the CPUs(212 a-212 b) to a centralized location (i.e., the adjustable resourcemanagement module (200)), which is smaller and less complex than thehandshaking logic required when resource management is handled bymultiple entities (e.g., multiple CPUs). Furthermore, some of thelower-level resource management tasks (e.g., freeing up the resource,pushing or pulling the resource as part of the allocation process, etc.)are offloaded to the adjustable resource management module (200),freeing up processing resources at the CPU and permitting less powerfuland/or smaller CPUs to be used in the system, if desired.

Returning briefly to FIG. 1, it is noted that an adjustable resourcemanagement module uses adjustable resource configuration information(see, e.g., step 102 in FIG. 1) and resource state information (see,e.g., step 104 in FIG. 1) in deciding whether to deny or grant aresource allocation request. The following figures describe moredetailed examples of these pieces of information and illustrate furtherbenefits associated with an adjustable resource management module (200).

FIG. 3 is a block diagram illustrating an embodiment of an adjustableresource management module. In some embodiments, the adjustable resourcemanagement module (200) in FIG. 2 is implemented as shown. In thisexample, the adjustable resource management module (300) includesadjustable resource configuration information (302), resource stateinformation (304), and a controller (306). In some embodiments, theadjustable resource configuration information (302) and/or resourcestate information (304) is/are stored on some memory in the adjustableresource management module (300).

The adjustable resource configuration information (302) describes anylimitations, such as minimums (e.g., a guaranteed number of resourcesthat are available to a given resource requestor, regardless of whatother resource requestors in that group have requested or been granted)or maximums (e.g., for a resource requestor individually or a groupcollectively) for the relevant resource. In some embodiments, one ormore resource requestors are grouped together and any grouped resourcerequestors must share resources with other resource requestors in thegroup; this grouping information may be stored in the adjustableresource configuration information (302). As implied by the name, anyinformation stored therein is adjustable (e.g., the resource requestorsin a given group can be changed, number of groups sharing the totalresources can be changed, a minimum can be changed, a maximum can bechanged, etc.). In some embodiments, a change in the number of groupscan be done (i.e., is permitted) when the system is in idle state (i.e.,no resources are outstanding). In some embodiments, the minimum andmaximum values for each type can be changed dynamically (e.g., even ifresources have been assigned but only under some conditions). Someexamples of adjustable resource configuration information and changes toit are described in more detail below.

The resource state information (304) records or otherwise reflects thecurrent (e.g., allocation) state of the resources. In some embodiments,in addition to recording what resources are currently allocated, someadditional information associated with the resource requestors is storedin the resource state information (e.g., a type identifier).

In order for a resource allocation request to be granted by theadjustable resource management module (300) (or, more specifically, thecontroller (306)), a necessary (but not necessarily sufficient)condition is that the resource state information (304) must indicatethat there is a sufficient number or amount of available (i.e.,unallocated) resources. Furthermore, another necessary (but notnecessarily sufficient) condition is that the request would not exceedany individual or group limitations (e.g., maximums) specified in theadjustable resource configuration information (302).

The following figure describes a more detailed example of the adjustableresource configuration information (302).

FIG. 4A shows two tables illustrating embodiments of adjustable resourceconfiguration information for hardware resources and firmware resources,respectively. In some embodiments, an adjustable resource managementmodule manages hardware and/or firmware resources and these tables showtwo examples of what the adjustable resource configuration informationmay include.

The top table (400) shows an example of adjustable resourceconfiguration information for hardware resources. In this example, thehardware resources being managed include a buffer (in this example with1,024 buffer slots which can be allocated in units of one or more uponrequest and grant) and RAID bins (in this example with 64 RAID binswhich can be allocated in units of one or more upon request and grant).

In this example, requests for buffer slots come from three resourcerequestors: the flash translation layer (FTL) (see the first row (420)),host writes (see the second row (422)), and host reads (see the thirdrow 424). For convenience, the type names (i.e., the names of theresource requestors) are shown in the second from left column (404) andtheir corresponding usage type identifiers (of Type_0, Type_1, andType_2, respectively) are shown in the leftmost column (402). The termsusage type identifiers, type identifiers, and resource requestors areused interchangeably herein.

As shown by the group identifier column (406), all three resourcerequestors (see rows 420, 422, and 424) are grouped together and havethe same group ID of Group_0, which is associated with the buffer. Forconvenience, the group name is included in the center column (408). Thethird from right column (410) shows that there is a limit of 1,024buffer slots that are available for the buffer group.

For context, the FTL table stores the physical-to-logical addressmapping that is stored in the shared buffer and therefore needs to beallocated buffer slots. For example, in FIG. 2, the host (204) uses alogical address but the storage (206) uses a physical address and amapping between the two is maintained. This mapping information is veryimportant and so the (e.g., guaranteed) minimum for the FTL table inthis example is the same value as the maximum.

Host writes (see row 422) is associated with write data from a host(e.g., 204 in FIG. 2). When a host (e.g., 204 in FIG. 2) sends writedata to the storage controller (e.g., 202 in FIG. 2) to be stored in thestorage (e.g., 206 in FIG. 2), the write data is stored temporarily inthe shared buffer and buffer slots may be requested for that purpose. Toensure that none of the traffic read or writes are starved, a smallbuffer pool is set as minimum for host writes, in this example a minimumof 64.

Host reads (see row 424) are associated with read requests from the host(e.g., 204 in FIG. 2). In some embodiments, the system pre-allocates thebuffer for read requests. Once the data is read back from (e.g., Flash)storage (e.g., 206 in FIG. 2), the read-back data can be store in thebuffer to be processed by the error correction code (ECC) engine tocorrect any bit errors in the read-back data. The buffer is emptied whenthe corrected data is sent to the host, thereby completing the readrequest.

The fourth row (426) in the top table (400) is associated with RAID bins(e.g., which hold program failure recovery data) and there is only oneresource requestor in that group. For example, a minimum resourcerequirement may prevent system deadlocks by ensuring that no processwhich requires access to the resource stalls for lack of resources.

As shown in the top table (400) and bottom table (450), in someembodiments, the resource (e.g., associated with the resource allocationrequest received at step 100 in FIG. 1) includes one or more of thefollowing: a hardware resource, a buffer in hardware, a RAID bin inhardware, a firmware resource, a front-end command in firmware, or aback-end command in firmware.

The minimum column (412) shows the minimum (i.e., guaranteed) number ofresources that a given resource requestor of the system is guaranteed(e.g., regardless of what other resource requestors in that group havebeen allocated).

The maximum column (414) shows the maximum number that a given resourcerequestor will be granted. In some applications, a maximum resourcelimit may be desirable because it prevents performance dips caused byresource hogging.

In some embodiments, while the minimum (412) is a guaranteed value thatthe system will always honor, the maximum (414) is not a guaranteedamount but is dependent upon the other resource requestors in the group.For example, if the other resource requestors in the group arerelatively inactive, then a maximum amount may be allocated or otherwisegranted to a resource type that is requesting resources. However, if theother resource requestors in the group are active, then the system maynot be able to allocate the maximum amount to a resource type that isrequesting resources.

Neither the group limit (e.g., in the limit column (410)) nor theindividual maximum (e.g., in the maximum column (414)) can be exceededwhen a resource allocation request is being considered. Likewise, arequest is not granted if the requested amount would prevent a (e.g.,guaranteed) minimum for another usage type identifier from beingsubsequently granted.

The bottom table (450) shows an example of adjustable resourceconfiguration information for firmware resources. As with the top table(400), the bottom table (450) has a usage type identifier column (452),a type name column (454), a group identifier column (456), a group namecolumn (458), a (group) limit column (460), a (usage type) minimumcolumn (462), and (usage type) maximum column (464).

It is noted that in this example, the group identifiers (406 and 456)are globally unique across both tables (400 and 450) but the usage typeidentifiers (402 and 452) are not necessarily unique between groups.

In this example, the firmware has two interfaces or sides: the front-end(e.g., facing host (204) in FIG. 2) and the back-end (e.g., facingstorage (206) in FIG. 2). Correspondingly, the firmware resources in thebottom table (450) are associated with front-end commands (e.g.,Group_2) and back-end commands (e.g., Group_3). The front-end commandgroup (i.e., Group_2) has two resource requestors: Host IO (see row 470)and ME host split (see row 472). The back-end command group (i.e.,Group_3) includes only a single resource requestor: BCMD (see row 474).

In one example of how an adjustable resource management module decideswhether to grant a resource allocation request (e.g., at step 106 inFIG. 1), all of the following conditions must be satisfied in order fora resource allocation request to be granted:

-   -   The group limit (410 or 460) for that group would not be        exceeded by the requested number of resources (e.g., taking into        account already-allocated resources for that group, recorded in        the allocation state information).    -   The maximum (414 or 464) for that resource requestor (i.e.,        usage type) would not be exceeded by the requested number of        resources (e.g., taking into account resources already-allocated        to that resource requestor, recorded in the allocation state        information).    -   All of the minimums (412 or 462) associated with other resource        requestors in the same group can still be satisfied or otherwise        met, even after allocating the requested number of resources        (e.g., taking into account already-allocated resources for other        resource requestors in that group, recorded in the allocation        state information).

As described in the above example, in some embodiments, the usage typeidentifier is associated with a first usage type and determining whetherto grant the resource allocation request (e.g., at step 106 in FIG. 1)includes considering whether allocating the requested amount wouldprevent a second usage type, having the same group identifier as thefirst usage type, from being allocated a second minimum associated withthe second usage type.

As indicated by its name, the resource configuration information (e.g.,400 and 450) is adjustable. In some embodiments, a new value is desiredto be written to the adjustable resource configuration information whichwould “break” or otherwise be inconsistent with the other values in thegroup. In some embodiments, the new value is verified or otherwisechecked before the new value is actually written to the adjustableresource configuration information. In one example, a new minimum valueis not permitted to be written to the adjustable resource configurationinformation if the sum of minimums for that group (including the desirednew minimum) would exceed the group limit. For example, by preventingthe update, this may communicate to the resource requestor that thesystem cannot honor the desired new minimum. Likewise, by verifying thata desired new maximum does not exceed the group limit, the system cancommunicate to a resource requestor when or if a desired new maximum cannever be honored.

As described above, in some embodiments, the process of FIG. 1 furtherincludes receiving a new value for the adjustable resource configurationinformation; determining whether the new value would violate a relatedvalue in the adjustable resource configuration information; and in theevent it is determined that the new value would violate the relatedvalue, discarding the new value without writing the new value to theadjustable resource configuration information.

Although not shown here, in some embodiments, a resource (e.g., thebuffer) is split amongst multiple groups, each with one or more usagetypes. In some applications, system components change and the associatedresources change. For example, a firmware upgrade may be performed whichchanges the number and/or types of available firmware resources (e.g., anew resource, an increased number of resources, etc.). Or, a module orblock (e.g., within a storage controller) is updated and the type and/ornumber or resources used by that block change, which changes the demandprofile. In some cases, the type of traffic moving through the systemchanges, which places different demands on firmware and/or hardwareresources (e.g., reading back badly degraded data from storage with manyerrors, putting a greater demand on the error correction decoder tocorrect the errors). In some applications, a hardware resource isupdated (e.g., a buffer is expanded so there are more slots). Suchchanges in the system can be more easily accommodated adapted to becauseof the adjustable nature of the resource allocation system describedherein.

As described above, in some embodiments, the process of FIG. 1 furtherincludes updating the adjustable resource configuration information witha new value, wherein the new value is associated with one or more of thefollowing: a new resource, an updated version of a (e.g., existing)resource, a new usage type, or an updated version of an existing usagetype.

FIG. 4B is a diagram illustrating an embodiment of a change to thenumber of usage types and groups. In this example, table 450 from FIG.4A is updated to the state shown here in table 480. For brevity, a usagetype identifier column is not shown in the example of table 480. In thisexample, a new type is added to Group_2: ME host split 2 (482) and forclarity ME host split (472 in FIG. 4A) is now labeled ME host split 1(484). To accommodate the new usage type in that group, an additional256 units of that resource has been added to Group_2 (see limit column486) and Group_3 has been eliminated (e.g., where the additional 256units of resource are taken from the now-eliminated Group_3 and aregiven to Group_2). In one example application, such situations may arisewhen the firmware scheme changes but there is no change to the hardware.

The following figure describes a more detailed example of resource stateinformation (e.g., 304 in FIG. 3).

FIG. 5 is a diagram illustrating an embodiment of resource stateinformation and associated allocation communications. In the exampleshown, table 500 shows an example of resource state information whichtracks the state of 2,048 units of a particular resource. The resourceidentifier column (502) includes an identifier for each resource. Theallocated column (504) tracks whether a particular resource has beenallocated. The type identifier column (506) tracks the type identifierof the resource requestor that has been allocated that resource (e.g.,assuming the corresponding allocated field is set to TRUE).

In this example, the type identifier (506) is stored in the resourcestate information (500) so that a mapping between the resourceidentifier and the type identifier exists and can be used subsequently.For example, consider how resource 0x000 (see row 508) is allocated.Resource allocation request (520) is sent by a resource requestor(having a type identifier of Type_1) to an adjustable resourcemanagement module (not shown). The resource allocation request (520)includes a header (522) that identifies the communication as a resourcerequest, the type identifier (524) of the resource requestor, and thegroup identifier (526) of the group to which the resource requestorbelongs. For brevity, a requested amount is not shown (or in someembodiments, a fixed or predefined amount is requested each time).

In response, the adjustable resource management module returns theresource allocation response (540) to the resource requestor. (Assumethat in this example, the minimum, maximum, and group limit checks haveall passed.) The resource allocation response (540) includes a header(542) identifying the communication as a resource allocation response,the resource identifier (544) of the resource(s) being allocated, andthe granted Boolean (546) indicating whether the request was granted ordenied. The top row (508) in the resource state information (500) isalso updated at this time to reflect the allocation of resource 0x000(column 502) to type identifier Type_1 (column 506) and the allocatedvalue (column 504) is set to TRUE.

When the resource requestor no longer needs the allocated resource, adeallocation message (560) is sent to the adjustable resource managementmodule which includes a header (562) identifying the communication as adeallocation message, the resource identifier (564) being deallocated,and the group identifier (566) of the resource requestor.

Note that the deallocation message (560) does not include the typeidentifier, so the adjustable resource management module would not beable to update its allocation counts of how many resources are currentlyallocated to each usage type based solely on the information included inthe deallocation message (560). However, because the type identifier(524) included in the request (520) is saved in the resource stateinformation (500) when resource 0x000 is allocated, the adjustableresource management module knows for which usage type to decrement theallocation count. Accurate and timely allocation counts are needed, forexample, to ensure that the minimums and/or maximums are not violated,nor are requests unnecessarily denied.

As shown in this example, in some embodiments, granting the resourceallocation request (e.g., at step 112 in FIG. 1) includes storing amapping between the usage type identifier and a resource identifier inthe resource state information.

In some embodiments, a deallocation message (e.g., 560) originates fromthe resource itself, as opposed to the resource requestor that wanted touse it. The following figure shows an example of this.

FIG. 6 is a diagram illustrating an embodiment of a deallocation messagethat originates from a resource. In the example shown, slots in thebuffer (604) are desired for a host write where the write data willeventually be written to storage (606). A CPU i (600), which acts as anintermediary of the host (610) and is one of a plurality of CPUs in thestorage controller (608), sends a resource allocation request to theadjustable resource management module (602). In this example, theadjustable resource management module (602) grants the request andreturns a resource allocation response to CPU i (600).

Once slots in the buffer (604) have been allocated, the host (610) sendshost write data to the buffer (604) to be stored in the allocated slots.The storage controller (608) sends the buffered write data from thebuffer (604) to the storage (606). In some cases, there may be other,earlier read or write instructions sent to the storage (606) that needto be executed before the buffered write data can be written to thestorage and therefore the write may not complete immediately.

Once the buffered write data has successfully been written to storage(606), a deallocation communication is sent (e.g., directly) to theadjustable resource management module (602) from the buffer (604) sothat the allocated slots in the buffer can be released as soon aspossible. In some embodiments, other components (e.g., hardware orfirmware CPU) other than the resource requestor can send a de-allocationrequest. In contrast, some other resource management systems onlyreceive deallocation communications from the resource requestor.However, this delays the deallocation of the buffer and/or is a lessefficient use of system resources.

For simplicity and ease of explanation, the deallocation communicationis shown in this example as originating from the buffer (604); thisassumes that the resource (in this example, the buffer) has sufficientstate information to know when to issue a deallocation communication(e.g., in this case, that the host write data has been successfullytransferred to storage (606) and the allocated buffer slots can befreed). In some applications, the buffer (or other resource) does notknow when the resource requestor is done with the allocated bufferslots. In some such embodiments, another module or block (such as anintermediary manager or controller and that is not the resourcerequestor) that manages or oversees the resource and has the appropriateknowledge or information to know when to issue a deallocationcommunication generates the deallocation communication and sends it tothe adjustable resource management module.

As shown in this figure, in some embodiments, the process of FIG. 1further includes: deallocating the requested amount of the resource inresponse to receiving a deallocation communication from the resource. Asdescribed above, in some embodiments, the process of FIG. 1 furtherincludes: deallocating the requested amount of the resource in responseto receiving a deallocation communication from the resource and updatingan allocation count associated with the usage type identifier, includingby accessing a mapping between a resource identifier and the usage typeidentifier that is stored in the resource state information (see, e.g.,the mapping that is stored in resource state information (500) in FIG.5).

Returning briefly to FIG. 4A, in some embodiments, some informationstored in adjustable resource configuration information is changed. Thefollowing figure describes one example about how an adjustable resourcemanagement module responds to or otherwise handles such a change.

FIG. 7 is a graph illustrating an embodiment of a maximum associatedwith a host write usage type that is adjusted. In this example, both themaximum (700) as well as the allocated number (702) for host writes areshown. At the beginning of the graph (e.g., before time t0 (704)), thehost write is allocated the maximum of 512 (e.g., of buffer slots) andtherefore the maximum (700) and the allocated number (702) are both 512.

At time t0 (704), the maximum (700) is reduced from 512 to 256. In thisexample, the already-allocated resources are “grandfathered in.” Thatis, the host write is permitted to retain its 512 allocated bufferslots, even though after time t0 (704), the allocated number (702) of512 exceeds the current maximum (700) of 256. This may be desirable insome applications since it permits the resource requestor to completeits process and/or usage of the allocated resource without anydisruption.

At time t1 (706), the resource requestor no longer needs the allocatedresource and a deallocation occurs, reducing the allocated number (702)from 512 to 0.

At time t2 (708), the resource requestor desires 512 buffer slots andrequests that amount. However, because the request amount is greaterthan the current maximum of 256, the request is denied.

As shown in this example, in some embodiments, the process of FIG. 1further includes: after the resource allocation request is granted,updating the maximum in the adjustable resource configurationinformation with a new maximum that is strictly less than the requestedamount, wherein the requested amount of the resource continues to begranted even after the adjustable resource configuration information isupdated with the new maximum.

In some embodiments, the usage of a resource is monitored and theresource configuration information is adjusted in real time to adapt tocurrent usage patterns or traffic. The following figure describes oneexample process of this.

FIG. 8 is a flowchart illustrating an embodiment of a process to adjustthe resource configuration information in response to real time usage.In some embodiments, the process is performed by one of the CPUs (212a-212 b) in FIG. 2. In some embodiments, the process is performed incombination with the process of FIG. 1.

At 800, a first allocated amount associated with a first usage typeidentifier and a second allocated amount associated with a second usagetype identifier are monitored, wherein the first usage type identifierand the second usage type identifier are associated with a same groupidentifier. For example, suppose the system is a storage system (see,e.g., FIG. 2) and the first usage type identifier is associated with(e.g., a host) writing to storage and the second usage type identifieris associated with (e.g., a host) reading from storage.

At 802, it is determined whether the first allocated amount satisfies alow activity test and the second allocated amount satisfies a highactivity test. For example, resource state information (e.g., 500 inFIG. 5) may be accessed to determine the amount of resources currentlyallocated to a particular usage type identifier. In some embodiments,the first allocated amount (e.g., a number of allocated buffer slots)satisfies a low activity test if it is less than some threshold (e.g.,using less than 10% or 5% of maximum for that usage type). Similarly,the second allocated amount may satisfy a high activity test if it isgreater than some threshold (e.g., using more than 90% or 95% of maximumfor that usage type). In some embodiments, the low activity test and/orthe high activity test take into account an allocated amount over somewindow of time.

If at least one of the tests is not satisfied (804) then monitoringcontinues (800). If both of the tests are satisfied (804) then a firstmaximum setting associated with the first usage type identifier isreduced at 806 and a second maximum setting associated with the secondusage type identifier is increased at 808. To put it another way, theadjustments to the first maximum setting and to the second maximumsetting are performed such that no minimum of the group is violated, andalso such that the sum of the new maximums for the usage types does notexceed the maximum for the group.

For example, suppose that the storage system shown in FIG. 2 switches toa state or mode where the host (204) is reading a significant amount ofinformation from the storage (206) and is doing few or no writes. Asshown in the example of FIG. 4A (see table 400), host writes (422) maybe in the same group as host reads (424) and therefore share bufferslots. During a heavy read and light write period, it may be desirableto increase the maximum for pre-reads and reduce the maximum for hostwrites since the system is doing so much reading and so little writing(or vice versa). Naturally, if the traffic and/or usage patterns were tosubsequently change, the resource configuration information could beadjusted again using real time information.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. An adjustable resource management system,including: a controller that is configured to: receive a resourceallocation request that includes a usage type identifier and requestedamount of a resource, wherein the usage type identifier is associatedwith a group identifier; access adjustable resource configurationinformation to obtain: (1) a maximum associated with the usage typeidentifier, (2) a minimum associated with the usage type identifier, and(3) a group limit associated with the group identifier; access resourcestate information; determine whether to grant the resource allocationrequest based at least in part on the maximum, the minimum, the grouplimit, and the resource state information; in the event it is determinedto grant the resource allocation request, grant the resource allocationrequest; and in the event it is determined to not grant the resourceallocation request, deny the resource allocation request; and a memorythat is configured to store the adjustable resource configurationinformation and the resource state information.
 2. The adjustableresource management system recited in claim 1, wherein the adjustableresource management system is implemented at least in part using one ormore of the following: an application-specific integrated circuit(ASIC), a field-programmable gate array (FPGA), or a general-purposeintegrated circuit.
 3. The adjustable resource management system recitedin claim 1, wherein the resource includes one or more of the following:a hardware resource, a buffer in hardware, a RAID bin in hardware, afirmware resource, a front-end command in firmware, or a back-endcommand in firmware.
 4. The adjustable resource management systemrecited in claim 1, wherein: the usage type identifier is associatedwith a first usage type; and determining whether to grant the resourceallocation request includes considering whether allocating the requestedamount would prevent a second usage type, having the same groupidentifier as the first usage type, from being allocated a secondminimum associated with the second usage type.
 5. The adjustableresource management system recited in claim 1, wherein the controller isfurther configured to: receive a new value for the adjustable resourceconfiguration information; determine whether the new value would violatea related value in the adjustable resource configuration information;and in the event it is determined that the new value would violate therelated value, discard the new value without writing the new value tothe adjustable resource configuration information.
 6. The adjustableresource management system recited in claim 1, wherein the controller isfurther configured to: update the adjustable resource configurationinformation with a new value, wherein the new value is associated withone or more of the following: a new resource, an updated version of theresource, a new usage type, or an updated version of an existing usagetype.
 7. The adjustable resource management system recited in claim 1,wherein granting the resource allocation request includes storing amapping between the usage type identifier and a resource identifier inthe resource state information.
 8. The adjustable resource managementsystem recited in claim 1, wherein the controller is further configuredto: deallocate the requested amount of the resource in response toreceiving a deallocation communication from the resource.
 9. Theadjustable resource management system recited in claim 1, wherein thecontroller is further configured to: deallocate the requested amount ofthe resource in response to receiving a deallocation communication fromthe resource; and update an allocation count associated with the usagetype identifier, including by accessing a mapping between a resourceidentifier and the usage type identifier that is stored in the resourcestate information.
 10. The adjustable resource management system recitedin claim 1, wherein the controller is further configured to: after theresource allocation request is granted, update the maximum in theadjustable resource configuration information with a new maximum that isstrictly less than the requested amount, wherein the requested amount ofthe resource continues to be granted even after the adjustable resourceconfiguration information is updated with the new maximum.
 11. Theadjustable resource management system recited in claim 1, wherein thecontroller is further configured to: monitor a first allocated amountassociated with a first usage type identifier and a second allocatedamount associated with a second usage type identifier, wherein the firstusage type identifier and the second usage type identifier areassociated with a same group identifier; determine whether the firstallocated amount satisfies a low activity test and the second allocatedamount satisfies a high activity test; and in the event the low activitytest and the high activity test are both satisfied: reduce a firstmaximum setting associated with the first usage type identifier; andincrease a second maximum setting associated with the second usage typeidentifier.
 12. A method, including: receiving a resource allocationrequest that includes a usage type identifier and requested amount of aresource, wherein the usage type identifier is associated with a groupidentifier; accessing adjustable resource configuration information toobtain: (1) a maximum associated with the usage type identifier, (2) aminimum associated with the usage type identifier, and (3) a group limitassociated with the group identifier; accessing resource stateinformation; determining whether to grant the resource allocationrequest based at least in part on the maximum, the minimum, the grouplimit, and the resource state information; in the event it is determinedto grant the resource allocation request, granting the resourceallocation request; and in the event it is determined to not grant theresource allocation request, denying the resource allocation request.13. The method recited in claim 12, wherein the method is performed atleast in part using one or more of the following: anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), or a general-purpose integrated circuit.
 14. Themethod recited in claim 12, wherein the resource includes one or more ofthe following: a hardware resource, a buffer in hardware, a RAID bin inhardware, a firmware resource, a front-end command in firmware, or aback-end command in firmware.
 15. The method recited in claim 12,wherein: the usage type identifier is associated with a first usagetype; and determining whether to grant the resource allocation requestincludes considering whether allocating the requested amount wouldprevent a second usage type, having the same group identifier as thefirst usage type, from being allocated a second minimum associated withthe second usage type.
 16. The method recited in claim 12, furtherincluding: receiving a new value for the adjustable resourceconfiguration information; determining whether the new value wouldviolate a related value in the adjustable resource configurationinformation; and in the event it is determined that the new value wouldviolate the related value, discarding the new value without writing thenew value to the adjustable resource configuration information.
 17. Themethod recited in claim 12, wherein granting the resource allocationrequest includes storing a mapping between the usage type identifier anda resource identifier in the resource state information.
 18. The methodrecited in claim 12, further including: deallocating the requestedamount of the resource in response to receiving a deallocationcommunication from the resource; and updating an allocation countassociated with the usage type identifier, including by accessing amapping between a resource identifier and the usage type identifier thatis stored in the resource state information.
 19. The method recited inclaim 12, further including: after the resource allocation request isgranted, updating the maximum in the adjustable resource configurationinformation with a new maximum that is strictly less than the requestedamount, wherein the requested amount of the resource continues to begranted even after the adjustable resource configuration information isupdated with the new maximum.
 20. The method recited in claim 12,further including: monitoring a first allocated amount associated with afirst usage type identifier and a second allocated amount associatedwith a second usage type identifier, wherein the first usage typeidentifier and the second usage type identifier are associated with asame group identifier; determining whether the first allocated amountsatisfies a low activity test and the second allocated amount satisfiesa high activity test; and in the event the low activity test and thehigh activity test are both satisfied: reducing a first maximum settingassociated with the first usage type identifier; and increasing a secondmaximum setting associated with the second usage type identifier.